Apple (NASDAQ:AAPL) stock's big gain recently will soon be put to the test. The tech giant just put a date to its fiscal first-quarter earnings release: Jan. 28. 

The pressure is on. The report trails a return to top- and bottom-line growth, the launch of new products and services, and a 90% gain in Apple's stock price over the last twelve months. In addition, there's the fact that Apple's fiscal first quarter is seasonally its biggest quarter every year.

Ahead of Apple's earnings release, here are some key items for investors to watch.

Apple CEO Tim Cook during the company's 2019 WWDC keynote presentation

Apple CEO Tim Cook. Image source: Apple.

Will revenue growth accelerate again?

After returning to top-line growth in its third quarter of fiscal 2019, squeaking by with a 1% year-over-year increase, the company managed to improve its revenue growth once again during fiscal Q4. Revenue increased 2% year over year during the period.

Can Apple keep up this momentum in fiscal Q1? Based on management's guidance for the important quarter, it's certainly possible. Apple said it expected revenue for the period to be between $85.5 billion and $89.5 billion. The midpoint of this guidance range implies 4% year-over-year revenue growth.

Given that Apple's revenue guidance is typically conservative, the tech giant is likely to see another period of accelerated growth. Although there are exceptions to the norm -- the tech giant missed its fiscal first-quarter guidance for revenue last year.

How is Apple's iPhone business faring?

Fiscal 2019 was a tough year for iPhone -- at least when compared to Apple's iPhone X-driven fiscal 2018. Total iPhone revenue in fiscal 2019 declined 14% year over year.

But the important segment started to show signs of improvement toward the end of the year. In fiscal Q4, for instance, iPhone revenue was down just 9% -- much better than a 15% decline across the first three quarters of fiscal 2019. In addition, Apple CEO Tim Cook said in the company's fiscal fourth-quarter earnings call that the launch of its newest iPhone models drove a "significant upswing in demand in the final part of the quarter."

Could iPhone revenue declines moderate even more in fiscal Q1 or -- even better -- return to growth?

Checking on wearables and services

Finally, investors will obviously want to check on the company's two biggest catalysts: services and wearables. Both Apple's services segment and its wearables, home, and accessories segment saw their already strong growth rates accelerate even more during fiscal Q4. Services revenue increased 18% year over year, and wearables, home, and accessories revenue jumped 54% year over year.

Investors should look to see if Apple was able to sustain these impressive growth rates during fiscal Q1.

Apple will report its fiscal first-quarter results after market close on Tuesday, Jan. 28. It will hold a conference call to discuss those results at 2 p.m. PT on the same day.